1. Field of the Invention
The present invention relates to a volume adjustment device for adjusting volume of an audio signal.
2. Description of the Related Art
There is a volume adjustment program that makes a smartphone, a tablet PC or the like function as a volume adjustment device for adjusting volume of an audio signal. For example, the volume adjustment program is integrated into a control program for operating an AV receiver from the smartphone. The smartphone into which the control program is installed communicates with the AV receiver wirelessly and controls the AV receiver. For example, the smartphone displays a slide bar at a display section to adjust volume of the audio signal that is output from the AV receiver to a speaker.
FIG. 12 illustrates an example that a conventional slide bar is displayed at the display section. The smartphone receives movement of a knob 100 by a touch panel interlocked with the display section. Position of the knob indicates volume value. The smartphone sends volume value corresponding to operation of the knob to the AV receiver. In this conventional example, in case that the user operates the knob by mistake, volume of the audio that is output from the AV receiver changes immediately. For this reason, there is possibility that loud audio that the user does not intend occurs.
In order to solve a problem above, in a device that is described in JP 3806610 B, as illustrated in FIG. 13, two knobs 101 and 102 are displayed at a display section. One knob 101 is a knob that a user can operate. The other knob 102 is a knob that indicates volume value. When the user operates the knob 101, the knob 101 moves according to the user's operation. The knob 102 follows the knob 101 that moves according to the user's operation with predetermined speed. After the user operates the knob 101, the user keeps touching the knob 101. When the knob 102 arrives at position of the knob 101, volume becomes volume that the user requests. After the user's operation of the knob 101, before the knob 102 arrives at position of the knob 101, the user leaves a finger from the knob 101. The knob 101 returns to the knob 102 that indicates volume value. Thus, even if the user moves the knob 101 widely by mistake, that loud audio output immediately is prevented.
In the device that is described in JP 3806610 B, there is a problem that the device cannot manage cases where the user would like to change volume quickly because increasing speed of the audio is always slow.